1. Field of the Invention
The present invention relates to a continuous element row for a slide fastener in which the element row being obtained by stamping a monofilament made of synthetic resin by using stamping rollers, and a method and an apparatus for producing the element row.
2. Description of the Related Art
Usage of this type of slide fastener has been further diversified in recent years, and the slide fastener has been frequently used not only for thin outerwear but also for extremely thin underwear in addition to conventional various bags, clothes, or industrial sheet material. Therefore, size and configuration of the elements are diversified and rigidity of the elements are also diversified.
This type of continuous elements obtained from the monofilament made of synthetic resin basically comprises coupling heads to be coupled with a mating element, a pair of upper and lower leg portions bent to extend from each coupling head, and connecting portions for connecting the upper and lower leg portions of adjacent element. Usually, each coupling head has at opposite sides thereof bulging portions, in a longitudinal direction of the element row, and the bulging portions enter gap portions between the upper and lower leg portions of the mating element to couple each other when the element row is coupled with the mating element row.
A coupling head is generally shaped by pressing a coupling portion of the monofilament made of synthetic resin with a pressing jig having a projecting streak so as to plastically deform the monofilament such that the monofilament is partially flattened, thereby forming the bulging portions at left and right portions of the monofilament. In a state wherein the element is bent to be attached to a fastener tape, a vertical sectional shape of the coupling head to the fastener tape is approximately an ellipse which is elongated vertically. If the gap between the upper and lower leg portions is large, the bulging portions of each coupling head can easily enter the gap, thereby enabling the element rows to be coupled with each other.
However, for the slide fastener described above, it has been desired that the fastener element be made thinner in order to improve touch and appearance. Therefore, in order to decrease heights of the elements projecting from the fastener tape face, the upper and lower leg portions of the elements are attached substantially in close contact with each other and in a state wherein the leg portions are regularly ordered. As a result, sufficient gaps can not be formed between the upper and lower leg portions, and the bulging portions of the coupling heads can not sufficiently enter the gaps. Therefore, necessary coupling function after the coupling can not be obtained in many cases.
If the bulging portions are formed smaller, particularly when the slide fastener is curved to project toward the element side, or when the slide fastener is twisted along a longitudinal direction, the slide fastener can not bear variation of pitches between the elements, and thus a coupling tends to split.